The present invention relates to a refrigeration lubricating oil. More particularly, this invention concerns a refrigeration lubricating oil composition comprising a branched-chain alkylbenzene component and a dialkyl sulfosuccinate component.
Branched-chain alkylbenzenes are widely used as lubricating oils for compressors in refrigerators. See, for example, U.S. Pat. Nos. 3,642,634; 3,733,850; 4,046,533; and 4,199,461. However, it has been found that the use of branched-chain alkylbenzenes as lubricating oils often causes compressors to run noisier than when using a naphthenic mineral lubricating oil. This is due, at least in part, to the lower foaming tendency of branched-chain alkylbenzenes, since foam is seen to behave as a noise insulator.
Japanese Pat. No. J58-069,298 discloses a lubricating oil for refrigerators which is described as a hard alkylbenzene type or ester type synthetic oil containing a silicone oil having a dimethyl polysiloxane structure. The addition of dimethyl polysiloxane to the synthetic oil is taught to cause frothing in the oil and a reduction in the noise of the compressor.